taming.c

语音压缩编码中的g729p编码程序

/*
   ITU-T G.729 Annex C - Reference C code for floating point
                         implementation of G.729
                         Version 1.01 of 15.September.98
*/

/*
----------------------------------------------------------------------
                    COPYRIGHT NOTICE
----------------------------------------------------------------------
   ITU-T G.729 Annex C ANSI C source code
   Copyright (C) 1998, AT&T, France Telecom, NTT, University of
   Sherbrooke.  All rights reserved.

----------------------------------------------------------------------
*/

/*
 File : TAMING.C
*/

/**************************************************************************
 * Taming functions.                                                      *
 **************************************************************************/
#include "typedef.h"
#include "ld8k.h"

static FLOAT exc_err[4];

void init_exc_err(void)
{
    int i;
    for(i=0; i<4; i++) exc_err[i] = (FLOAT)1.;
    return;
}

/**************************************************************************
* routine test_err - computes the accumulated potential error in the     *
* adaptive codebook contribution                                         *
**************************************************************************/
int test_err( /* (o) flag set to 1 if taming is necessary  */
    int t0,       /* (i) integer part of pitch delay           */
    int t0_frac   /* (i) fractional part of pitch delay        */
)
{
    
    int i, t1, zone1, zone2, flag;
    FLOAT maxloc;
    
    t1 = (t0_frac > 0) ? (t0+1) : t0;
    
    i = t1 - L_SUBFR - L_INTER10;
    if(i < 0) i = 0;
    zone1 = (int) ( (FLOAT)i * INV_L_SUBFR);
    
    i = t1 + L_INTER10 - 2;
    zone2 = (int)( (FLOAT)i * INV_L_SUBFR);
    
    maxloc = (FLOAT)-1.;
    flag = 0 ;
    for(i=zone2; i>=zone1; i--) {
        if(exc_err[i] > maxloc) maxloc = exc_err[i];
    }
    if(maxloc > THRESH_ERR) {
        flag = 1;
    }
    return(flag);
}

/**************************************************************************
*routine update_exc_err - maintains the memory used to compute the error *
* function due to an adaptive codebook mismatch between encoder and      *
* decoder                                                                *
**************************************************************************/

void update_exc_err(
    FLOAT gain_pit,      /* (i) pitch gain */
    int t0             /* (i) integer part of pitch delay */
)
{
    int i, zone1, zone2, n;
    FLOAT worst, temp;
    
    worst = (FLOAT)-1.;
    
    n = t0- L_SUBFR;
    if(n < 0) {
        temp = (FLOAT)1. + gain_pit * exc_err[0];
        if(temp > worst) worst = temp;
        temp = (FLOAT)1. + gain_pit * temp;
        if(temp > worst) worst = temp;
    }
    
    else {
        zone1 = (int) ((FLOAT)n * INV_L_SUBFR);
        
        i = t0 - 1;
        zone2 = (int)((FLOAT)i * INV_L_SUBFR);
        
        for(i = zone1; i <= zone2; i++) {
            temp = (FLOAT)1. + gain_pit * exc_err[i];
            if(temp > worst) worst = temp;
        }
    }
    
    for(i=3; i>=1; i--) exc_err[i] = exc_err[i-1];
    exc_err[0] = worst;
    
    return;
}